JPS6314796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vent device for a control rod drive mechanism of a boiling type nuclear reactor, which facilitates the removal of internal air after initial assembly or disassembly inspection of the control rod drive mechanism.

Conventional control rod drive mechanism air bleeding work (hereinafter referred to as
This is called venting work. ) was not only time consuming and difficult to schedule for periodic inspections and disassembly, but also caused radiation exposure problems during venting work. That is, FIG. 1 shows the main parts of the control rod drive mechanism, and a conventional vent mechanism will be explained.

A housing 1 of the control rod drive mechanism has a thermal sleeve 2 attached to the inner surface, and an upper control rod guide 3.
The control rod 4 is placed on top. A coupling socket 5 is formed at the lower end of the control rod 4, and a plug 6 is housed in the center thereof, urged downward by a spring 6a. A coupling spud 7 is inserted into the coupling socket 5 and cooperates with the plug 6 to form a coupled state. When the uncoupling rod 8 extending below the plug 6 is pushed upward and the coupling spud 7 is pulled downward, the coupling is released.

Inside the housing 1 is an index tube 10.
is housed therein, has the above-mentioned coupling spud 7 at its upper end, and moves up and down. index tube 1
A piston tube 14 is further inserted into the piston 0 with an annular gap (extraction side cylinder chamber) 24 provided therein. The upper end of the piston tube 14 is closed by a stop piston 13, and an inner filter 9 is placed on top of the stop piston 13. The stop piston 13 and the inner filter 9 closely slide on the index tube 10 and slidably support the top of the index tube 10. 11 and 11 are seal rings, and 12 is a spring washer.

Further, as shown in FIGS. 1 and 6, an annular elevating piston 31 is fixed to the lower inner surface of the index tube 10, and the inner surface of the elevating piston 31 is slidably fitted into the piston tube 14. Further, a bushing 32 and a seal ring 33 are fitted to the elevating piston 31. The piston tube 14 extends downward through the lifting piston 31, and its lower end is attached to the control rod drive mechanism housing 1.

An insertion side cylinder chamber 34 is provided on the lower surface of the lifting piston 31, and this insertion side cylinder chamber 34
The index tube 10 is raised by supplying working water to the index tube 10. On the other hand, when lowering, the working water rises from below the housing 1 through the gap between the piston tube 14 and the indicator tube 15 and enters the inner cavity 23. Subsequently, the working water passes through the orifice 22 and enters the gap (extraction side cylinder chamber) 24, acts on the upper surface of the lifting piston 31, and lowers the index tube 10. By raising and lowering the index tube 10, the control rods 4 are connected,
Liberation takes place.

That is, the connection of the control rod 4 is such that when the index tube 10 is raised, the coupling spud 7 enters the coupling socket 5 while pushing up the plug 6, and the plug 6 descends downward by the spring 6a. It is carried out by. Also,
To release the control rod 4, the entire piston tube 14 is mechanically pushed up, the uncoupling rod 8 is raised above the inner filter 9, the plug 6 is lifted above the coupling spud 7, and at the same time the index tube 10 is This is done by lowering the

When newly assembling this control rod drive mechanism, or when disassembling and inspecting it during periodic inspection and reassembling it,
Remove internal air and fill with working water.

If air is present in the control rod drive mechanism, the pressure caused by the working water becomes unstable when the control rod is withdrawn, and the control rod cannot be withdrawn stably and smoothly. To prevent this, air is vented when assembling the control rod drive mechanism. This work cannot be completed in a short time. During assembly, the index tube 10 is at the lowest position, and by supplying working water, the index tube 10 is first raised, the control rod 4 is inserted, and then the vent is performed by pulling out and inserting the tube. However, on the insertion side, the index tube 10 is at the lowest position (fully withdrawn position), and there is little air pocket in the insertion side cylinder chamber below the lifting piston, so that venting can be completed in a short time. However, in the drawing side cylinder,
Air exists in the gap 24 and the inner cavity 23 of the piston tube 14, and is pushed by the working water rising from below and accumulates in the upper part, requiring a long time for venting. Occasionally, during venting work, there was a problem where the vent could not be removed due to insufficient venting.

In view of the current situation, the present invention provides a venting device for a nuclear reactor control rod drive mechanism that can reliably perform extraction side venting in a short time and eliminate troubles during venting work.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The structure of the control rod drive mechanism is the same as that of the conventional one, and the same parts are designated by the same reference numerals as those used in FIG. 1, and explanations of the structure and operation will be omitted.

A vent passage 25 is provided that passes through the head of the piston tube 14, the stop piston 13, and the inner filter 9 and communicates upward from the inner cavity 23 of the piston tube 14, and a valve chamber 26 is provided in a part of the vent passage 25.
A ball valve 16 as a lower check valve is pressed by a spring 17 on a valve seat 27 below the valve chamber 26, and a poppet valve 18 as an upper check valve is pressed on an upper valve seat 28 by a spring 17. The valve stem 19 connected to the pouch valve 19 is connected to the vent passage 25a.
The distal end 19a is loosely inserted into the inner filter 9 and protrudes from the upper surface of the inner filter 9, facing the lower end of the uncoupling rod 8.

That is, the vent passage 25 is provided with upper and lower check valves in series to allow inflow from each side. The form of the check valve is free, and two valve chambers may be provided, each with a pressing spring.

The pressing force of the poppet valve 18 is set to the pressing force of the spring 17 so that when it collides with the uncoupling rod 8, it is pushed open. The lower end of the anchor rod 8 has a groove 20 for letting air escape in the radial direction.

Next, the action will be explained.

When the control rod drive mechanism is initially assembled or disassembled and reassembled for periodic inspection, the control rod 4 is uncoupled and the index tube 10 is lowered (the state shown in FIG. 3.5). At this time, the uncouple rod 8 is pushed down by the spring 6a, pushing down the valve stem 19 and stopping on the upper surface of the inner filter 9. Poppet valve 18 is open.

In this state, perform air venting on the extraction side. When the working water is supplied by the withdrawal operation, the working water rises in the piston tube inner cavity 23 and reaches the orifice 22.
pass through and enter the gap (extraction side cylinder chamber) 24,
Press down the lifting piston. However, the index tube 10 is in the fully retracted position and does not move. In this way, the pressure in the inner cavity 23 and the gap 24 increases, and the ball valve 16 serving as the lower check valve is pushed open by overcoming the force of the spring 17 (FIG. 5).

At this time, since the poppet valve 18 serving as an upper check valve is open, air and working water above the piston tube 14 flow from the valve chamber 26 to the valve stem 19.
It passes through the gap between the vent passage 25a and is discharged upward from the groove 20.

After venting on the extraction side is completed in this way, the index tube 10 is raised and coupled to the control rod 4 by the operation on the insertion side. (Status shown in Figures 2 and 4). Due to the coupling, the uncoupling rod 8 is slightly raised and separated from the inner filter 9, and the poppet valve 18 is closed. As for the venting on the insertion side, since the index tube 10 is in the fully withdrawn position and there is little air pocket, the venting work can be easily completed by this operation.

In the control rod withdrawal operation during operation, the operating water pressure for lowering the index tube 10 is applied to the poppet valve 18, so even if the anchor rod 8 comes into contact with the valve stem 19, the poppet valve 18 will not move. will not open. That is, the ball valve 16 and the poppet valve 18 serve as a mutual check, and there is no problem with control rod operation.

As described above, the vent device for the reactor control rod drive mechanism of the present invention has a vent passage provided at the tip of the piston tube, and two upper and lower check valves that allow flow from each side in series in this passage. The check valve is designed to be pushed open by colliding with the uncoupling rod when the control rod is uncoupled, and venting is performed by withdrawing working water at the control rod fully withdrawn position immediately after assembly. As a result, venting work on the extraction side, which conventionally took a very long time, can be completed in a short period of time, simplifying the regular inspection schedule, and reducing the radiation exposure of workers involved in venting work. It is a unique feature that has great effects, such as solving problems such as the inability to pull out due to insufficient venting.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional control rod drive mechanism, FIGS. 2 and 3 are longitudinal sectional views showing an embodiment of the control rod drive mechanism equipped with the vent device of the present invention, and FIG. Figure 3 shows the state when the control rod is inserted and pulled out, Figures 4 and 5 are enlarged longitudinal cross-sectional views of the main parts when the control rod is inserted and pulled out, corresponding to Figures 2 and 3, respectively. FIG. 2 is a vertical cross-sectional view showing a lower portion of a conventional control rod drive mechanism. 4...Control rod, 5...Coupling socket, 6...
Plug, 7... Coupling spud, 8... Uncoupling rod, 9... Inner filter, 10... Index tube, 11, 13... Stop piston, 14... Piston tube, 16... Ball valve,
17... Spring, 18... Poppet valve, 19... Valve stem, 20... Concave groove, 23... Piston tube inner cavity,
24... Gap, 25, 25a... Vent passage, 26...
Valve chamber.

Claims (1)

[Scope of Claims] 1. An index tube provided with a coupling at the upper end and an annular lifting piston at the lower part; the lower end is attached to the control rod drive mechanism housing; It is composed of a piston tube with a stop piston mounted thereon, and is controlled by raising and lowering the index tube by working fluid acting on the lower surface of the lifting piston and working fluid acting on the upper surface of the lifting piston through the inner cavity of the piston tube. In a control rod drive mechanism that is designed to be attached to and detached from the lower end of the rod, a vent passage is provided that passes through the stop piston up and down,
This vent passage is equipped in series with an upper check valve that allows air and some working water to flow in from below, and a lower check valve that allows air to flow in from below. 1. A vent device for a nuclear reactor control rod drive mechanism, characterized in that the vent device is forcibly released by an anchor pull rod when in a withdrawn state. 2. The upper check valve is provided with a valve stem that is loosely inserted into the vent passage, the upper end of the valve stem projects upward and faces the lower end of the anchor rod, and a groove is provided on the lower end surface of the anchor rod. A vent device for a nuclear reactor control rod drive mechanism according to claim 1. 3. The reactor control rod drive according to claim 1, characterized in that the spring that presses the upper check valve is set so that the check valve pushes up but does not have enough force to push up the anchor rod. Mechanism venting device. 4. A vent device for a nuclear reactor control rod drive mechanism as set forth in claim 1, wherein the upper and lower check valves are pressed in the closing direction by a spring loaded between them.